Zentropy Theory for Positive and Negative Thermal Expansion
Zentropy Theory for Positive and Negative Thermal Expansion
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DOI：
10.1007/s11669-022-00942-z
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发表时间：
2021-07
影响因子：
1.4
通讯作者：
Zi-kui Liu;Yi Wang;S. Shang
中科院分区：
文献类型：
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作者：
Zi-kui Liu;Yi Wang;S. Shang
在天然和人造材料中都观察到，体积有时会随着温度的升高而减小。虽然对某些个别材料已经有了机械上的理解，但对“为什么体积有时会随着温度的升高而减小”这一问题的一般性回答是：仍然缺乏。基于体积对温度的导数，即，热膨胀等于熵对压力的负导数，我们发展了一个多尺度熵的一般理论来理解和预测作为温度函数的体积变化，这在本工作中被称为z熵理论。结果表明，在高温下的相是基态稳定和多个非基态亚稳组态的统计表示。结果表明，当高几率非基态组态的体积小于基态组态的体积时，在一定的温压组合范围内，相的体积随温度的升高而减小，在临界点处表现出负的热膨胀发散性.作为例子，预测的热膨胀的正和负的分歧，分别在临界点的Ce和Fe 3 Pt，沿着的温度和压力范围异常的正和负的热膨胀。作者认为，由于熵的变化驱动着系统对外界刺激的响应，因此z熵理论也适用于预测相的其它物理性质的反常。
It has been observed in both natural and man-made materials that volume sometimes decreases with increasing temperature. Though mechanistic understanding has been gained for some individual materials, a general answer to the question “Why does volume sometimes decrease with the increase of temperature?” remains lacking. Based on the thermodynamic relation that the derivative of volume with respect to temperature, i.e., thermal expansion, is equal to the negative derivative of entropy with respect to pressure, we developed a general theory in terms of multiscale entropy to understand and predict the change of volume as a function of temperature, which is termed as zentropy theory in the present work. It is shown that a phase at high temperatures is a statistical representation of the ground-state stable and multiple nonground-state metastable configurations. It is demonstrated that when the volumes of the nonground-state configurations with high probabilities are smaller than that of the ground-state configuration, the volume of the phase may decrease with the increase of temperature in certain ranges of temperature-pressure combinations, depicting the negative divergency of thermal expansion at the critical point. As examples, positive and negative divergencies of thermal expansion are predicted at the critical points of Ce and Fe3Pt, respectively, along with the temperature and pressure ranges for abnormally positive and negative thermal expansions. The authors believe that the zentropy theory is applicable to predict anomalies of other physical properties of phases because the change of entropy drives the responses of a system to external stimuli.